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Ring buffer based queuing utility for applications that require high performance and/or a small footprint. Well suited for embedded and stream based processing.

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package com.javanut.pronghorn.pipe.util.hash;

import java.util.Arrays;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Non-Thread safe simple fast hash for int to int mapping.
 * 
 * No set is allowed unless no previous value is found.
 * To change previous value replace must be called.
 * Remove can not be supported.
 * Key must not be zero.
 * 
 * @author Nathan Tippy
 *
 */
public class IntHashTable {

	private static final Logger logger = LoggerFactory.getLogger(IntHashTable.class);
	
	public static IntHashTable EMPTY = new IntHashTable(0);
	
	private final int mask;
	private final long[] data;
	private int space;
	private final int bits;
	
	public static IntHashTable newTableExpectingCount(int count) {		
		return new IntHashTable((int) (1+Math.ceil(Math.log(count)/Math.log(2)) ));
	}
	
	public IntHashTable(int bits) {
		this.bits = bits;
		int size = 1<> 32);
	}

	private static long scanForItem(int key, int mask, int hash, long[] data2, long block) {
		
		while ((block != 0) && ((int)block) != key) { 			
			block = data2[++hash & mask];
		}
		return block;
	}
	    
	public static boolean hasItem(IntHashTable ht, int key) {

		int mask = ht.mask;
		int hash = MurmurHash.hash32finalizer(key);
		long block = ht.data[hash & mask];
		while (((int)block) != key && block != 0) { 			
			block = ht.data[++hash & mask];
		}
		return 0!=block; 
	}
	
	public static boolean replaceItem(IntHashTable ht, int key, int newValue) {

		int mask = ht.mask;
		int hash = MurmurHash.hash32finalizer(key);
		int temp = (int)ht.data[hash&mask];//just the lower int.
		while (temp != key && temp != 0) { 			
			temp = (int)ht.data[++hash & mask];
		}
		if (0 == temp) {
			return false; //do not set item if it does not hold a previous value.
		}
		
		long block = newValue;
		block = (block<<32) | (0xFFFFFFFF&key);
		ht.data[hash&mask] = block;
		return true;
	}
	
   public static void visit(IntHashTable ht, IntHashTableVisitor visitor) {
	   int j = ht.mask+1;
	   while (--j >= 0) {
		   long block = ht.data[j];
		   if (0!=block) {
			   int key = (int)block;
			   int value = (int)(block>>32);			   
			   visitor.visit(key,value);
		   }		   
	   }	   
   }	
   
   public static IntHashTable doubleSize(IntHashTable ht) {
	   IntHashTable newHT = new IntHashTable(ht.bits+1);
	   int j = ht.mask+1;
	   while (--j >= 0) {
		   long block = ht.data[j];
		   if (0!=block) {
			   int key = (int)block;
			   int value = (int)(block>>32);
			   setItem(newHT, key, value);
		   }		   
	   }	   
	   assert(newHT.space>0);
	   return newHT;
   }
	
}